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Does My Water Heater Need an Expansion Tank? A Minneapolis-St. Paul Plumber Answers

Even though it sounds like something you install if you want more hot water, an expansion tank actually serves another purpose: it helps relieve pressure in a hot water system.

If you’re wondering whether you need an expansion tank, here’s the bottom line: If your home has a “closed” loop system, then it will need an expansion tank.

We know you probably have more questions.

In this blog, we’ll explain the following:

What is a closed-loop system (and why it requires an expansion tank)

How to verify you have a closed-loop plumbing system

Want a Minneapolis-St. Paul plumber to install an expansion tank for you? We can do it for you!

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What is a closed-loop system

Homes either have an open or closed-loop plumbing system. A closed-loop system prevents water from flowing in the reverse direction.

This means water that enters your home can’t go back into the city lines once it flows into your home’s pipes. For obvious public health reasons, new homes usually have a closed-loop system, which means chances are, you’ll need an expansion tank.

Why a closed-loop system requires an expansion tank

When water is heated inside your water heater, then water expands and pressure increases inside the tank. This is called thermal expansion. 

The expanded water raises the pressure inside the tank; which, if left unchecked, can cause your water heater to burst.

In an open plumbing system, water can go out the way it came into the water heater, via the cold water inlet pipe. However, since a closed-loop system creates a single path for water to enter (but not exit), this extra water will need somewhere to go.

That’s where the expansion tank comes in. When the pressure inside your water heater gets too high, the extra water volume goes into the expansion tank to relieve the pressure in the main tank. 

Because it greatly increases the lifespan of your tank, most manufacturers require your water heater to have an expansion tank in order for the warranty to be valid. 

Now, we’ll help you know how to determine if you have a closed-loop system.

How to verify you have a closed-loop system

If you want to double-check and verify you have a closed-loop system, look for a backflow prevention device on your home’s water main line.

Here’s why: A backflow prevention device stops water from exiting your home’s water main line, which is a sure-fire sign your home has a closed-loop plumbing system. 

So, where can you find this backflow prevention device?

A backflow prevention device is always connected to the main water shutoff valve. You can usually find the main water shutoff valve in the basement or on the perimeter of the house. 

The backflow prevention devices vary in design, but some look like a large, circular component in the middle of the pipe.

Note: If you’re having trouble locating the backflow prevention device, contact a professional for assistance. 

Need an expansion tank? Let a Twin Cities plumber install one for you

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We’ve served Minneapolis-St. Paul residents for over 100 years, making sure their plumbing needs are met. We can give you an upfront, honest quote on the cost to install an expansion tank, and can usually get the job done the same day.

Visit our plumbing service page to see other plumbing services we offer.